1. Field of the Invention
This invention relates to an image processing apparatus removing a background color contained in color image data.
2. Description of Related Art
Image processing technology has been known in which image data are corrected upon conversion from color space of such as, e.g., RGB or CMYK as device-depending color to color space of, such as, e.g., CIEXYZ as a color mode of device-independent color. With such technology, a correction of the whole color space in maintaining its color balance is made upon white point conversion from the XYZ value of a certain reference color (e.g., white color displayed on a monitor) to the XYZ value of another reference color (e.g., white color of printing medium).
With such image processing technology, Japanese Patent Application Publication No. 2001-320598 has a description on a color correction apparatus correcting color to be outputted to an output device in accordance with light of an environment at which a monitor or printing medium is located.
In modern image processing technology, however, image processing is made at CIEL*a*b* color space as a type of uniform color space in which components of the brightness and chromaticity (colorfulness) are independent in color models representing color space and in which differentials of numerical values are close to human's perception, and background removing processing has been known as a representative art.
The background removing processing generally includes processing to convert the brightness value L* of the background component corresponding to the background color into the maximum value and to make the value of the chromaticity a*b* closer to zero, thereby rendering the background color the white color as the achromatic color of the brightest brightness.
This method, however, raises a problem that distortions and deviations may occur in color space of corrected results thereby to lose color balance, because the L* value, a* value, and b* value of the background color component are corrected in the same way to pixels forming the components other than components of the background color.